In recent years, there has been an increasing demand for narrowing of picture frames of, in particular, display devices for mobile uses. Various techniques have been proposed for achieving the narrowing of picture frames. An example of such proposed techniques is a technique in which silicon dioxide is deposited and patterned, thereby forming double spacer walls, and a sealant is disposed between these spacer walls.
In modern display devices for mobile uses, an increase in fineness has been advanced, and such a design is required that the active area becomes larger and the picture frame portion of the peripheral area becomes narrower. Thus, in order to secure an aperture ratio (an area contributing to display) per pixel, it is dispensable to provide an optical layer (or an organic insulation film for planarizing a surface) immediately below a pixel electrode. Since this optical layer is used also as a protection layer of a driver which is disposed outside the active area, this optical layer is disposed also on the peripheral area.
In the meantime, in many cases, an aluminum (Al)-based wiring material is used for the wiring of display devices. Such a wiring material tends to be easily corroded due to the effect of moisture, etc. Of various resin-based materials (e.g. the above-described optical layer or alignment films) for use in display devices, some materials which are applied have water permeability. Thus, a wiring, which is formed of an aluminum-based wiring material, tends to be easily corroded due to moisture which permeates through the resin-based material. Such corrosion of various wirings leads to degradation in reliability, and may cause deterioration in display quality with the progress of corrosion.